In a few short weeks, the "Arrow" spin-off "The Flash" will begin production with hopes for it to debut as its own series in the fall of 2014. We've heard some things from the "Arrow" team about what to expect from the sibling series, but in a recent interview, executive producer Greg Berlanti laid out the differences between the two series going forward.

"Barry (Grant Gustin) is different from Oliver (Stephen Amell)," he told Digital Spy. "He's a man of science and has more of a sci-fi bent, whereas Arrow has a bit more of a crime bent…We often talk about how Oliver comes off like a pessimist, but deep down he's an optimist and has hope. Barry lost his mother at a very young age, his father was sent to prison for murdering his mom, he went through a lot of stuff – on the surface he's bubbly and upbeat and seems like an optimist, but deep down maybe there's no hope left….So they're a really nice contrast to each other and the show functions in that way, I think. Certainly in the pilot script Barry has an effervescence and a lightness, but there's still a dark well beneath that."

Berlanti also reiterated that we'll be seeing way more super powered characters on "The Flash," and the we've only seen the beginning of S.T.A.R. Labs.

"We've talked a lot on Arrow about the particle collider and Harrison Wells and S.T.A.R. Labs and so you'll see S.T.A.R. Labs as an active part of the show."

In the event that "The Flash" pilot isn't picked up to series, Berlanti says they'd likely try and keep Grant Gustin on "Arrow."

"Fingers crossed we don't screw it up and he gets his own show! If he didn't, I don't think we would ever want to let Grant go. He's too valuable. That would be our hope, I think – no matter what, to keep Barry part of the universe."

Set to star Grant Gustin as Barry Allen, the cast for "The Flash" has expanded significantly in the past weeks to include Candice Patton as Iris West, Jesse L. Martin as Iris's father Detective West, Rick Gosnett as Detective Eddie Thawne (aka Professor Zoom), Danielle Panabaker as Caitlin Snow (aka Killer Frost), and Carlos Valdes as Cisco Ramon (aka Vibe).

"The Flash" arrives from co-creators Greg Berlanti and Andrew Kreisberg who, along with Geoff Johns, will write the pilot episode with "Arrow" pilot director David Nutter at the helm.